This invention relates to electrical switches and more particularly to an electrical switch applicable for use on automotive steering columns.
The automobile today is a complex machine having numerous electrically controlled devices. The operator of the vehicle must be able to control these devices from his seated position without having to awkwardly reach for the many control switches or levers. Thus, it has become increasingly useful to provide electrical switches and controls on the steering column.
One type of steering column switch is illustrated in German Pat. No. 28 28 592. In this Patent there is disclosed a steering column switch having a rotary pin aligned parallel to the steering spindle. The rotary pin is held between socket plates and has an annular ring slider encompassing the steering spindle. A switching lever extends perpendicular from the steering spindle which carries and operates the ring slider. There is a passageway through the annular ring slider through which the rotary pin extends. The switching lever and annular ring slider can be tilted around a tilting axis that is perpendicular to and crosses the axis of the rotary pin. The ring slider is shifted on the rotary pin in the pin's axial direction to control the electrical switching. The ring slider has a stop profile diametrically opposite the steering column from the axial pin. The stop profile is provided with a stop spring which exerts a force against the ring slider.
The ring slider control of this type is used mainly for controlling wiper functions in the automobile. The tilting movement of the ring slider causes it to assume two tilting positions. In one position the washing of the windshield could occur and in a second position, the rear windshield washers or other second function, can occur.
The problem with the switch illustrated in German Pat. No. 28 28 592 is that the contact devices in this Patent are of the lift-off contact type. In such a design the contacts make and break by having the contact areas substantially parallel to each other, and when the contacts are moved adjacent each other, the contact areas touch and complete a circuit. To break the circuit, the contact areas are separated. This type of contact device is not a preferred contact design in that arcing occurs in the contact area, the contacts can become tarnished or have an oxide build-up, and they are not self-cleaning. A preferred type of device is the sliding contact which has the contact areas slide over each other when making or breaking contact. This provides a self-wiping or cleaning action in the contact area. However, on the ring slider as illustrated in the German Patent it is very difficult to provide sliding contact devices which operate from a tilting movement without providing for specially designed mechanical linkages and sliders to achieve this type of switching. This would unduly complicate the design and increase the cost of the switch. Due to the very limited space which is available on a steering column switch, even in the peripheral direction, extra mechanically linked pieces are extremely undesirable. Most of these types are practically unusable in that they would take up too much room on the steering column.